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03/16/2016

The resident bird gets the butterfly.

When you look around you might notice birds going about their daily business. But what are they up to?

American redstarts are migratory birds that travel to Jamaica during the winter and potentially compete with resident birds, like the Yellow Warbler, for food. Photo by Dave Inman. CC By-NC-ND 2.0

It’s likely that they are foraging—looking for something to eat. Perhaps you’ve never thought much about what birds eat, but there’s a lot more to it than just worms, as the popular expression suggests. Many birds are insectivorous, meaning that they eat arthropods, a broader taxonomic group that includes insects and spiders (among other invertebrates).

As part of a Smithsonian sponsored project, I am collaborating with Luke L. Powell and Peter P. Marra of the Migratory Bird Center, Robert C. Fleischer of the Center for Conservation and Evolutionary Genetics, and Delano S. Lewis at Northern Caribbean University in Mandeville, Jamaica, to investigate the diets of insectivorous birds, as well as the poorly known but amazingly diverse community of Jamaican arthropods.

Our goal is to understand diet competition among resident Caribbean birds, and the millions of other birds that migrate to the Caribbean each winter. Specifically, we are studying two species, the yellow warbler (Setophaga petechia) and the American redstart (Setophaga ruticilla), at a long-term ecological research site at Font Hill Nature Preserve, Jamaica. In order to do this we are using cutting-edge, next-generation sequencing technology to sequence part of a gene (cytochrome oxidase I) of all arthropod diet items that have passed through the bird digestive tract and are excreted in their feces. We sequence all of the arthropods in the feces simultaneously, using a recently developed approach known as metabarcoding. We can then match the DNA sequences we obtain back to those of the arthropods living in the area, and figure out what the birds are actually eating.

Luke Powell using an aspirator to collect tiny beetles that have fallen onto a white shower curtain after vigorously shaking forest vegetation. Photo by Andreanna Welch

The little that we know about Jamaican arthropods suggests that they are very diverse. For example, even though Jamaica is 1/10 the size of Cuba and 1/7 the size of Hispaniola, the island has 20 species of jumping spiders, 45 species of fireflies, 20 species of butterflies and 6 species of ants that are found nowhere else in the world. However, Jamaican arthropods in general have not been studied extensively, and there are very few DNA sequences available in online databases, such as the Barcode of Life database, to which we could match the diet item sequences.

Delano Lewis, a Jamaican entomologist, uses the sweep net to sample arthropods from higher up in the forest canopy. Photo by Luke Powell.

The goal of our GGI funded project is to survey Jamaican arthropods in the Font Hill Nature Preserve to create a set of arthropod museum vouchers, collect genomic-quality samples, and obtain DNA barcode sequences for each species that we collect.

Black-light trapping a diverse array of moths, beetles, and other species. Photo by Luke Powell.

This will be important for understanding the biodiversity of the arthropod community there, and providing a baseline for future studies on the impacts of humans and global climate change. The information and samples collected during our study will also be an important resource for entomologists examining the evolutionary relationships of arthropods in Jamaica and elsewhere in the world. Beyond all this, the DNA sequences we obtain will help us to gain a better understanding of how bird species with similar diets are able to co-exist during the winter, which is one of the most food-limited times of year.

By Andreanna J. Welch, Research Associate at the Center for Conservation and Evolutionary Genetics in the Smithsonian Conservation Biology Institute (edited by GGI Staff).